Multi-carrier (MC) High-Speed Packet-Access (HSPA) is currently being standardized by the 3rd-Generation Partnership Project (3GPP). In the 3GPP's so-called Release 8 specifications, downlink packet communication using two adjacent HSPA carriers is supported. In the uplink, for the time being, only single-carrier transmissions are possible, but there is a 3GPP work item aiming at including communication using two adjacent uplink HSPA carriers in Release 9. In the work item, the carriers are intended to operate as legacy carriers to as large an extent as possible. Future 3GPP releases can be expected to evolve MC-HSPA in several ways, including support for more than two carriers and operation in different frequency bands. Furthermore, it may be desired to evolve the standard to further optimize the performance of a multi-carrier system.
As wireless networks continue to evolve to carry more packet data, while carrying less circuit switched data, it is quite likely that that one or more supplementary carriers in an MC-HSPA system will carry packet data exclusively. Consequently, it makes sense to optimize these carriers for packet data-only transmission. Today, however, the 3GPP standards for Wideband Code-Division Multiple Access (WCDMA) are sub-optimal for packet data-only transmission, particularly with respect to the uplink. Specifically, although the 3GPP specifications today (Release 7) support data rates of up to 11.52 megabits-per-second (Mbps) in the uplink, realizing such a high rate is challenging in practice. In fact, even a data rate of 4 Mbps is considered challenging today. A fundamental issue is that the power received at the base station (or “Node B”, in 3GPP terminology) needs to be at a very high level when a high data rate is used. However, a high received power level from a data user generally results in significant interference and degraded performance for important control channels that support the data service. To combat this increased interference and alleviate degraded control channel performance, user terminals may try to increase their transmit power levels. However, such actions may give rise to an unstable system, as the system's rise-over-thermal (RoT) metric can become out of control.